Summary Plants of Spartina anglica, Limonium vulgare, Armeria maritima and Glaux maritima were collected in the field and grown on different concentrations of NaCl, KCl and CaCl2. Salt secretion, ion content, water content and transpiration rates were determined. The highest sodium secretion was found in Spartina anglica, a species from the most saline habitat; and a somewhat lower secretion rate in Limonium vulgare. The lowest rates were found in Glaux maritima and Armeria maritima. The sodium secretion efficiency, i.e. the ability to maintain an unchanged internal sodium content, was highest in Spartina anglica. Spartina anglica is the most successful in the removal of excessively absorbed salt, since it secretes 60% of the absorbed sodium. The values for Limonium vulgare, Glaux maritima and Armeria maritima were 33, 20 and 4% respectively. The species studied differ in the preferential sequence of ion secretion as well as in secretion rate and efficiency. This preferential sequence of ion secretion seems to be similar in members of the same taxonomic group (Plumbaginaceae). The comparability of the secretion parameters is discussed with regard to morphological differences between the species.

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The extensive characterization of plant genes and genome sequences summed to the continuous development of biotechnology tools, has played a major role in understanding biological processes in plant model species. The challenge for the near future is to generate methods and pipelines for an efficient transfer of this knowledge to economically important crops and other plant species. In the case of flower bulbs, which are economically very important for the ornamental industry, flowering time control and vegetative propagation constitute the most relevant processes for agronomical improvements. Those processes have been reasonably studied in reference species, making them excellent candidates for translational investigations in bulbous plant species. The approaches that can be taken for the transfer of biological knowledge from model to non-model species can be roughly categorized as "bottom-up" or "top-down". The former approach usually goes from individual genes to systems, also known as a "gene-by-gene" approach. It assumes conservation of molecular pathways and therefore makes use of sequence homology searches to identify candidate genes. "Top-down" methodologies go from systems to genes, and are e.g. based on large scale transcriptome profiling via heterologous microarrays or RNA sequencing, followed by the identification of associations between phenotypes, genes, and gene expression patterns and levels. In this review, examples of the various knowledge-transfer approaches are provided and pros and cons are discussed. Due to the latest developments in transgenic research and next generation sequencing and the emerging of systems biology as a matured research field, transfer of knowledge concerning flowering time and vegetative propagation capacity in bulbous species are now within sight.

Salt secretion, salt accumulation and transpiration were simultaneously measured in salt-secreting and non-salt-secreting halophytes and glycophytes. The sodium content of the xylem sap was calculated. It is concluded that salt-secreting halophytes differ considerably in their sodium secretion rates, but less in their sodium exclusion capacity. Salt-sensitivity of the non-secreting species was related to a comparatively high sodium xylem content (15.1 mM Na). Transpiration rates are remarkably similar for all species. It is argued that the distinction between salt accumulators and salt excluders is not only based on differences in ion exclusion but is also related to the capacity to accumulate compatible osmotic solutes.In experiments aiming at an ecophysiological comparison of the mineral and water economy in relation to halophyte zonation, secretion, accumulation of sodium and transpiration were simultaneously measured in four salt-secreting and four non-salt-secreting halophytes and glycophytes. Plants were grown in a greenhouse (20°C, 65% RH; 6-18 hr light 7000Lux) in 0.25 strength Hoagland's solution with 0.2 M NaCI added. Salt secretion was measured by rinsing the leaves with distilled water over a 6 day period. Relative humidity of the air was kept at 65% in order to avoid the loss of secreted salt through run-off from the leaves,which occurs under more humid conditions (ROZEMA & RIPHAGEN 1977). Transpiration rates were determined by weight measurement for a 48 hr period. The total weight of the plants which were precultured for four weeks on NaCIfree0.25 strength Hoagland increased only slightly during the 6 day period. After harvesting and drying, the sodium content of the whole plant was determined by flame emission spectrophotometry. The sodium content of the xylem sap was calculated from the equation: . t ti I secretion + accumulation Ion concen ra IOn xy em sap = -----' ---------transpirationThe results are summarized in table 1, and it may be concluded that even the glycophytic species Juncus articulatus has the ability to exclude sodium ions to some extent since the rooting medium concentration (200 mM Na) is ten times reduced. In the non-secreting halophyte Juncus maritimus the sodium content of the xylem sap is even a factor 150 lower than that of the culture medium.Obviously the stronger exclusion of sodium ions in Juncus maritimus relates to its

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